Turbomachine rotor



Nov. 25, 1952 F. SCHAER 2,619,318

TURBOMACHINE ROTOR Filed June 7, 1947 2 SHEETS-SHEET 1 INVENTOR fzA/vz Ira/45R A ATTORN Nov, 25, 1952 SCHAER 2,619,318

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If AW ATTORNE Patented Nov. 25, 1952 TURBOMACHINE ROTOR Franz Schaer, Ober-Winterthur, Switzerland, as-

signor to Sulzer Freres, Socit Anonyme Application June 7, 1947, Serial No. 753,230 In Switzerland June 7, 1946 3 Claims.

The present invention relates to an axial flow turbomachine such as a compressor, blower, or turbine, and more particularly to a rotor and the blading of such a machine.

An object of the invention is the provision of a turbomachine in which the runner and/ or guide blades are mounted serially in helical grooves on the peripheral surface of a suitable cylindrical or conic body. A blade of one blade row is mounted in the same groove as a blade of another blade row. The blades are arranged in groups constituting stages of the turbomachine and the blades of each group are arranged in a plane which is at a right angle to the longitudinal axis of the cylindrical body, the latter forming with the blades thereon the rotor of the turbomachine. The blades of difierent groups or rows are spaced or separated by spacer members inserted in the grooves between the blades of different rows.

Another object of the invention resides in the provision of a method of producing the blades as well as blade spacer members as needed for a construction as specified in the paragraph next above. This method is characterized by the fact that a plurality of blades or spacer members are cut from helical portions left, of a rotund body after a plurality of helical grooves have been milled into the surface of said body.

The angle of inclination of the helices employed in the aforesaid machine and manufacturing method is preferably substantially like the angle enclosed by the chord of the base section of a blade and a plane which is at right angle to the axis of the machine in which the blades are used. Accordin to the invention the roots of at least a portion of the blades extend longitudinally substantially parallel to said chord and the thickness of the neck interconnecting the root and the blade proper is about equal to the greatest height of the section of the blade proper at its base.

According to the invention the blades are machined from a tubular or conic and hollow body the wall thickness of which is at least equal to the height of the blade root plus that of the blade proper. The outside diameter of said body corresponds to the outside diameter of the blade rows fitted on the rotor. The spacer members or blocks are made similarly from a round hollow body Whose wall thickness is at least equal to the height of the blocks and whose outside diameter corresponds substantially to that of the blade drum 1. e. the aforesaid cylindrical body, on which the spacers are used.

Since the walls of the grooves on the body for holding the blades follow helical or screw lines and the foot portions of the blades fit snugly into the grooves, the walls of the grooves, as well as the surfaces of the foot portions, are curved in three directions in contradistinction to conven- 2 tional designs in which such walls and surface are either straight or curved in two direction only.

Further and other objects of the present invention will be hereinafter set forth in the accompanying specification and claims and shown in the drawings which, by way of illustration, show what I now consider to be a preferred embodiment of my invention.

In the drawings:

Fig. l is a side view of a turbine rotor according to the invention with a number of blades removed and showing one blade in section;

Fig. 2 is an end view of the rotor shown in Fig. 1 with an end cover and a number of turbine blades removed;

Fig. 3 is a transverse sectional view of a turbomachine blade according to the invention, the section being taken adjacent to the neck of the blade, the neck being the portion between the root and the blade proper.

Fig. 4 is a perspective view of a blank with a plurality of spiral grooves milled thereinto for producing blanks of turbomachine blades according to the invention;

Fig. 5 is a perspective view of an individual blade blank according to the invention;

Fig. 6 is a perspective view of a finished blade according to the invention, with the outline of the blank from which it was made in dash and dot lines;

Fig. '7 is a perspective view of a finished spacer member according to the invention with the web portion with which it was connected to the body from which it was made indicated in dash and dot lines.

Like parts are designated by like numerals in all figures of the drawings.

Referring more particularly to Figs. 1 and 2, the rotor of the machine accordin to the invention is provided with helical or screw-shaped grooves l into which the roots of the blades 2 forming blade groups or rows 3 are inserted. There are as many grooves as there are blades in a row and all rows have the same number of blades. Neighboring blades in the same groove are separated by spacer members 4 which determine at the same time the distance between two blade rows. The ends of the grooves are closed by annular members 5 connected to the faces of the rotor drum.

The pitch angle a of the helical grooves is about equal to the angle s between the chord B of the section at the base of the blade and a plane 8 which is positioned at a right angle to the rotor axis 1, as is illustrated in Figs. 1 and 3. This makes it possible to place the blade roots of at least some of the blades substantially parallel to the chord of the section of the blades at their bases whereby the width or thickness b of the root is not much greater than the greatest height h of said base section. A blade root of this type can be made very light without sacrificing strength of its connection with the blade proper. The neck which connects the root with the blade proper is subjected primarily to tensile stresses. Depending on the flow conditions of the medium in which the buckets operate, the sections transverse to the longitudinal axis at the outer'parts of the blade are twisted relatively to the section at the base of the blade.

Fig. 4 illustrates a blank 9 having a central bore from which blades according to the invention are machined according to the process forming part of my invention. The outside diameterof the tubular body 9 is slightly larger than the outer diameter of a'blade row in which the finished blades will be used. Helical or screwshaped grooves l l are milled into the outer surface of body 9. The configuration of the milling cutters and of the produced grooves is such that the-remaining helical or screw-shaped portions 12 have the final shape of the neck 20 and of the root 2| of the blades to be produced, one being shown in Fig. 6. The remaining helical portions are then divided by cutting the body in planes I4 which are at 'a'right angle with respect to the axis 13 of the body. By cutting through the bridge portions [5, the blade blanks are separated from their supporting drum [6. The so produced blanks must then be machined down to the desired final blade configuration.

Fig.5 shows a blade blank as separated from the drum- I 6. At first the rest of the bridge portion 15 is removed for obtaining the final configuration of blade root 2l. This root can now be used for clamping the rough blade into the milli-ngmachine for forming the final shape of theblade proper. This is preferably done on a copying milling machine where the portions shown in dash-dot lines in Fig. 6 are removed. What remains is the finished blade comprising the blade proper l8, the neck and the foot or root 2!.

The spacer members, one of which is illustrated in Fig. '7, are made similarly as the blades, from a tubular body. The spacer member has, like the blade, a neck-23 and a root 24 from which, after separation of the spacer member from its drum, the bridge or web portion [5 only must be removed.

The guide blades which are inserted into the interior of the housing may be made in a similar manner'as the rotor blades. They are cut out of the interior of a tubular body instead of the exterior and are inserted in spiral grooves in the inner surface of the casing of the turbomachine. This way of mounting the blades and spacer members produces a very strong connection because the roots of the blades extend along the chord of the sections of the blades at their bases. The guide blades as well as the moving blades according to the present invention are light and yet very strong because the connection between the blade proper and its root amounts to a full section of the blade at its base and there is an almost straightfiow of the stresses. The blade support is weakened by only very small grooves leaving substantial portions of supporting material therebetween.

With blades according to the invention, the blade roots, .as well as the grooves into which they are fitted, are formed along cylindrical helical lines .;of constant pitch. If the lengths of the blades of different stages of the turbomachine differs considerably, the hollow body from which they are made may have the form of a cone. The body from which rotor blades are made need not be hollow but could be solid.

While I believe the above described embodi- 1 ment of my invention to be a preferred embodiment, I wish it to be understood that I do not desire to be limited to the exact details of method, design and construction shown and described, for

obvious modifications will occur to a person skilled in the art.

I claim:

1. A rotor for an axial flow turbomachine, comprising a cylindrical, one piece blade holder bodyhaving a cylindrical surface portion, a'plurality of continuous, parallel, and circumferentially spaced grooves in said surface portion; said grooves having walls following screw lines of constant pitch in said surface portion, and a plurality of blades individually having root portions having surfaces curved to conform with the screw lines followed by the walls of said grooves, a plurality of said blades being serially fitted with their root portions into each of said continuous grooves, the pitch of said groove being substantially the same as that defined for said blades by the flow conditions of the medium flowing through the turbomachine.

2. A rotor for an axial flow turbomachine, comprising a cylindrical, one-piece blade holder body having a cylindrical surface portion, a plurality of continuous, parallel, and spaced grooves in said surface portion, said grooves having walls following screwlines of constant pitch in said surface portion, and a plurality of blades individually having root portions having surfaces conforming with portions of the Walls of said grooves, a plurality of said blades being serially fitted with their root portions into each of said continuous grooves, said blades being arranged in parallel rows on the cylindrical surface of the rotor, each row being placed in a plane extending at a right angle to the rotation axis of the rotor, and the blades of one row being individually fitted into different continuous grooves.

3. A rotor as defined in claim 2, comprising spacer members conforming with the root portions of said blades and being serially fitted into said grooves alternately with the blades in the grooves for axially spacing said blade rows.

FRANZ SCHAER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Nov. 3, 1900 

